1. Field of the Invention
The present invention relates to an apparatus for making contact prints, and more particularly to an apparatus which makes prints by placing a sensitive sheet in contact with a negative and exposing the same to light through the negative. Hereinafter, the apparatus will be referred to as the "printing apparatus".
2. Description of the Prior Art
There are a variety of printing apparatus known in the art, among which are those disclosed in Japanese Patent Publication (examined) No. 61-38455 and Utility Model Publication (unexamined) No. 56-10624. The basic structure of the present invention is in common with these known apparatus, and to explain the background of the present invention, it will be described by reference to prior art FIG. 5 herein.
The example in the illustration is a vacuum type device, which comprises a printing box 1, a printing plate 2 having a soft sheet, and a frame 4 pivotally connected to the box 1 by hinges 3, the frame 4 including a transparent plate 5 such as glass. The printing plate 2 is provided with a packing 7 at its periphery, whereby when the frame 4 is placed over the printing plate 2, the optical seal therebetween is secured. The reference numeral 11 denotes a handle.
In addition to the hinges 3, the frame 4 and the box 1 are connected to each other by gas springs 8, whereby the opening and closing of the frame 4 is facilitated. When the frame 4 is placed over the printing plate 2, a confined space is formed therebetween. The air inside the confined space is removed by a vacuum pump (not shown) through bores 9. There is provided a source of light 10 above the frame 4.
A sensitive sheet is placed on the printing plate 2, and a negative is overlaid on the sensitive sheet. The frame 4 is placed over the printing plate 2. Then the vacuum pump is driven to evaculate the air from the confined space between the frame 4 and the printing plate 2, thereby securing a tight contact between the sensitive sheet and the negative at vacuum. Then the source of light 10 is illuminated, thereby projecting the image in the film onto the sensitive sheet.
A disadvantage of this type of printing apparatus is that the inner surface of the transparent plate 5 is liable to become stained with ink, an adhesive or dirt floating in air. A stain on the transparent plate 5 causes a pinhole and spoils the formation of an image. Consequently, a constant care is required such as by wiping or applying a cleanser, to keep the inner surface of the transparent plate 5 clean. On the other hand, a stain on the outer surface of the transparent plate 5 does not so seriously affect the formation of an image as on the inner surface, because of the fact that light is diffused during passage through the transparent plate 5 (normally 5 mm thick). Any stain on the outer surface has only to be brushed. No troublesome taking-care is necessary.
An elaborate maintenance procedure is required for keeping the inner surface of the transparent plate 5 clean. Particularly a large-scale apparatus will require a lot of labor; for example, when the transparent plate 5 is as large as 1.5 m.sup.2 in area, the lower portion of the transparent plate 5 is out of reach from the front side (indicated by arrow (A)) of the apparatus. As a result, the alternative way is to clean the transparent plate 5 from either side indicated by arrow (B). However, when the apparatus is crowded by other office furniture, access to the sides of the device is difficult if not impossible.